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Adnan Yaqub,Syed Atif Pervez,Umer Farooq,Mohsin Saleem,도칠훈,You-Jin Lee,Minji Hwang,Jeong-Hee Choi,Doohun Kim 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.3
A new conductive material, copper/Super-P carbon black composite (Cu-SPB), is prepared viaan efficient ion reducing method for use in low-temperature lithium-ion batteries (LIBs). Thepresent study investigated the effects of copper content on the low-temperature performance ofLIBs. Electrodes prepared with a high-copper-content conductive material (Cu = 18.54%) showedremarkably improved performance in terms of capacity retention (around 40%), cycling stability, andcolumbic efficiency. The electrochemical impedance spectroscopy (EIS) analysis revealed that thepresence of higher Cu contents could reduce the cell’s impedance. The results were also confirmedby using a coin-type full cell’s improved capacity retention, which indicated the significance of Cuparticles in enhancing the low-temperature performance of LIBs.
Pervez, Syed Atif,Kim, Doohun,Farooq, Umer,Yaqub, Adnan,Choi, Jung-Hee,Lee, You-Jin,Doh, Chil-Hoon American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.14
<P>This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li<SUP>+</SUP> ions diffusivity and electron transport.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-14/am501370f/production/images/medium/am-2014-01370f_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am501370f'>ACS Electronic Supporting Info</A></P>
Improved Performance of Ag-nanoparticle-decorated TiO2 Nanotube Arrays in Li-ion Batteries
Syed Atif Pervez,Umer Farooq,Adnan Yaqub,Chil-Hoon Doh,김두헌,심성주,황민지,최정희,이유진 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.9
The present work investigates the electrochemical response of silver nanoparticle (Ag-NP)-decorated TiO2 nanotube (NT) layers as an anode material for a lithium-ion battery. Self-organizednanotube layers with a thickness of approximately 1 µm and a diameter of approximately 100nm were grown by anodization of Ti in a fluoride-containing aqueous electrolyte. Ag NPs (averageparticle size of ~ 10 nm) were deposited both inside and outside the nanotube geometry ina well-distributed manner through a simple and efficient photocatalytic reduction process. Themorphology and the chemical composition of the resulting materials were characterized by usingfield-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and energy dispersiveX-ray spectroscopy (EDX). Our results show that the TiO2 NT layers decorated with Ag NPshad a superior electrochemical response in terms of charge/discharge capacity, rate capability, cyclicperformance and columbic efficiency. The enhanced performance is attributed to the improved electronicand ionic conductivity, obtained by providing highly conductive paths to electrons flowingthrough a well-distributed Ag NPs deposition on the walls of the highly-oriented NTs.
Electrically exploded silicon/carbon nanocomposite as anode material for lithium-ion batteries.
Farooq, Umer,Choi, Jeong-Hee,Kim, Doohun,Pervez, Syed Atif,Yaqub, Adnan,Hwang, Min-Ji,Lee, You-Jin,Lee, Won-Jae,Choi, Hae-Young,Lee, Sang-Hoon,You, Ji-Hyun,Ha, Chung-Wan,Doh, Chil-Hoon American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.12
<P>In this work, silicon (Si) containing carbon coated core-shell nanostructures were synthesized by electrical explosion of Si wires in ethanol solution followed by high energy mechanical milling (HEMM) process. Material characterization was carried-out using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. HEMM led to very fine and amorphous Si particles in the presence of carbon and inactive Silicon-Carbide (SiC) matrix. These Si based nanocomposites, obtained through electrical explosion followed by HEMM (milled sample), exhibited enhanced electrochemical performance than unmilled nanocomposites, when evaluated as anode material for lithium-ion batteries (LIBs). On completion of (the) 1st cycle, milled and unmilled sample(s) showed specific discharge capacities around 825 mAh/g and 717 mAh/g, respectively. Interestingly, the coulombic efficiencies of milled and unmilled samples were 98.5% and 97% after 60th cycle respectively. The enhanced electrochemical performance is attributed to fine and amorphous Si based nanocomposite obtained through HEMM process.</P>